swift/doc/source/deployment_guide.rst

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================
Deployment Guide
================
-----------------------
Hardware Considerations
-----------------------
Swift is designed to run on commodity hardware. At Rackspace, our storage
servers are currently running fairly generic 4U servers with 24 2T SATA
drives and 8 cores of processing power. RAID on the storage drives is not
required and not recommended. Swift's disk usage pattern is the worst
case possible for RAID, and performance degrades very quickly using RAID 5
or 6.
------------------
Deployment Options
------------------
The swift services run completely autonomously, which provides for a lot of
flexibility when architecting the hardware deployment for swift. The 4 main
services are:
#. Proxy Services
#. Object Services
#. Container Services
#. Account Services
The Proxy Services are more CPU and network I/O intensive. If you are using
10g networking to the proxy, or are terminating SSL traffic at the proxy,
greater CPU power will be required.
The Object, Container, and Account Services (Storage Services) are more disk
and network I/O intensive.
The easiest deployment is to install all services on each server. There is
nothing wrong with doing this, as it scales each service out horizontally.
At Rackspace, we put the Proxy Services on their own servers and all of the
Storage Services on the same server. This allows us to send 10g networking to
the proxy and 1g to the storage servers, and keep load balancing to the
proxies more manageable. Storage Services scale out horizontally as storage
servers are added, and we can scale overall API throughput by adding more
Proxies.
If you need more throughput to either Account or Container Services, they may
each be deployed to their own servers. For example you might use faster (but
more expensive) SAS or even SSD drives to get faster disk I/O to the databases.
Load balancing and network design is left as an exercise to the reader,
but this is a very important part of the cluster, so time should be spent
designing the network for a Swift cluster.
.. _ring-preparing:
------------------
Preparing the Ring
------------------
The first step is to determine the number of partitions that will be in the
ring. We recommend that there be a minimum of 100 partitions per drive to
insure even distribution across the drives. A good starting point might be
to figure out the maximum number of drives the cluster will contain, and then
multiply by 100, and then round up to the nearest power of two.
For example, imagine we are building a cluster that will have no more than
5,000 drives. That would mean that we would have a total number of 500,000
partitions, which is pretty close to 2^19, rounded up.
It is also a good idea to keep the number of partitions small (relatively).
The more partitions there are, the more work that has to be done by the
replicators and other backend jobs and the more memory the rings consume in
process. The goal is to find a good balance between small rings and maximum
cluster size.
The next step is to determine the number of replicas to store of the data.
Currently it is recommended to use 3 (as this is the only value that has
been tested). The higher the number, the more storage that is used but the
less likely you are to lose data.
It is also important to determine how many zones the cluster should have. It is
recommended to start with a minimum of 5 zones. You can start with fewer, but
our testing has shown that having at least five zones is optimal when failures
occur. We also recommend trying to configure the zones at as high a level as
possible to create as much isolation as possible. Some example things to take
into consideration can include physical location, power availability, and
network connectivity. For example, in a small cluster you might decide to
split the zones up by cabinet, with each cabinet having its own power and
network connectivity. The zone concept is very abstract, so feel free to use
it in whatever way best isolates your data from failure. Zones are referenced
by number, beginning with 1.
You can now start building the ring with::
swift-ring-builder <builder_file> create <part_power> <replicas> <min_part_hours>
This will start the ring build process creating the <builder_file> with
2^<part_power> partitions. <min_part_hours> is the time in hours before a
specific partition can be moved in succession (24 is a good value for this).
Devices can be added to the ring with::
swift-ring-builder <builder_file> add z<zone>-<ip>:<port>/<device_name>_<meta> <weight>
This will add a device to the ring where <builder_file> is the name of the
builder file that was created previously, <zone> is the number of the zone
this device is in, <ip> is the ip address of the server the device is in,
<port> is the port number that the server is running on, <device_name> is
the name of the device on the server (for example: sdb1), <meta> is a string
of metadata for the device (optional), and <weight> is a float weight that
determines how many partitions are put on the device relative to the rest of
the devices in the cluster (a good starting point is 100.0 x TB on the drive).
Add each device that will be initially in the cluster.
Once all of the devices are added to the ring, run::
swift-ring-builder <builder_file> rebalance
This will distribute the partitions across the drives in the ring. It is
important whenever making changes to the ring to make all the changes
required before running rebalance. This will ensure that the ring stays as
balanced as possible, and as few partitions are moved as possible.
The above process should be done to make a ring for each storage service
(Account, Container and Object). The builder files will be needed in future
changes to the ring, so it is very important that these be kept and backed up.
The resulting .tar.gz ring file should be pushed to all of the servers in the
cluster. For more information about building rings, running
swift-ring-builder with no options will display help text with available
commands and options. More information on how the ring works internally
can be found in the :doc:`Ring Overview <overview_ring>`.
----------------------------
General Server Configuration
----------------------------
Swift uses paste.deploy to manage server configurations. Default configuration
options are set in the `[DEFAULT]` section, and any options specified there
can be overridden in any of the other sections.
---------------------------
Object Server Configuration
---------------------------
An Example Object Server configuration can be found at
etc/object-server.conf-sample in the source code repository.
The following configuration options are available:
[DEFAULT]
================== ========== =============================================
Option Default Description
------------------ ---------- ---------------------------------------------
swift_dir /etc/swift Swift configuration directory
devices /srv/node Parent directory of where devices are mounted
mount_check true Whether or not check if the devices are
mounted to prevent accidentally writing
to the root device
bind_ip 0.0.0.0 IP Address for server to bind to
bind_port 6000 Port for server to bind to
workers 1 Number of workers to fork
================== ========== =============================================
[object-server]
================== ============= ===========================================
Option Default Description
------------------ ------------- -------------------------------------------
use paste.deploy entry point for the object
server. For most cases, this should be
`egg:swift#object`.
log_name object-server Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
log_requests True Whether or not to log each request
user swift User to run as
node_timeout 3 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
network_chunk_size 65536 Size of chunks to read/write over the
network
disk_chunk_size 65536 Size of chunks to read/write to disk
max_upload_time 86400 Maximum time allowed to upload an object
slow 0 If > 0, Minimum time in seconds for a PUT
or DELETE request to complete
================== ============= ===========================================
[object-replicator]
================== ================= =======================================
Option Default Description
------------------ ----------------- ---------------------------------------
log_name object-replicator Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
daemonize yes Whether or not to run replication as a
daemon
run_pause 30 Time in seconds to wait between
replication passes
concurrency 1 Number of replication workers to spawn
timeout 5 Timeout value sent to rsync --timeout
and --contimeout options
stats_interval 3600 Interval in seconds between logging
replication statistics
reclaim_age 604800 Time elapsed in seconds before an
object can be reclaimed
================== ================= =======================================
[object-updater]
================== ============== ==========================================
Option Default Description
------------------ -------------- ------------------------------------------
log_name object-updater Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
interval 300 Minimum time for a pass to take
concurrency 1 Number of updater workers to spawn
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
slowdown 0.01 Time in seconds to wait between objects
================== ============== ==========================================
[object-auditor]
================== ============== ==========================================
Option Default Description
------------------ -------------- ------------------------------------------
log_name object-auditor Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
interval 1800 Minimum time for a pass to take
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
================== ============== ==========================================
------------------------------
Container Server Configuration
------------------------------
An example Container Server configuration can be found at
etc/container-server.conf-sample in the source code repository.
The following configuration options are available:
[DEFAULT]
================== ========== ============================================
Option Default Description
------------------ ---------- --------------------------------------------
swift_dir /etc/swift Swift configuration directory
devices /srv/node Parent directory of where devices are mounted
mount_check true Whether or not check if the devices are
mounted to prevent accidentally writing
to the root device
bind_ip 0.0.0.0 IP Address for server to bind to
bind_port 6001 Port for server to bind to
workers 1 Number of workers to fork
user swift User to run as
================== ========== ============================================
[container-server]
================== ================ ========================================
Option Default Description
------------------ ---------------- ----------------------------------------
use paste.deploy entry point for the
container server. For most cases, this
should be `egg:swift#container`.
log_name container-server Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
node_timeout 3 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
================== ================ ========================================
[container-replicator]
================== ==================== ====================================
Option Default Description
------------------ -------------------- ------------------------------------
log_name container-replicator Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
per_diff 1000
concurrency 8 Number of replication workers to
spawn
run_pause 30 Time in seconds to wait between
replication passes
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external
services
reclaim_age 604800 Time elapsed in seconds before a
container can be reclaimed
================== ==================== ====================================
[container-updater]
================== ================= =======================================
Option Default Description
------------------ ----------------- ---------------------------------------
log_name container-updater Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
interval 300 Minimum time for a pass to take
concurrency 4 Number of updater workers to spawn
node_timeout 3 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
slowdown 0.01 Time in seconds to wait between
containers
================== ================= =======================================
[container-auditor]
================== ================= =======================================
Option Default Description
------------------ ----------------- ---------------------------------------
log_name container-auditor Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
interval 1800 Minimum time for a pass to take
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
================== ================= =======================================
----------------------------
Account Server Configuration
----------------------------
An example Account Server configuration can be found at
etc/account-server.conf-sample in the source code repository.
The following configuration options are available:
[DEFAULT]
================== ========== =============================================
Option Default Description
------------------ ---------- ---------------------------------------------
swift_dir /etc/swift Swift configuration directory
devices /srv/node Parent directory or where devices are mounted
mount_check true Whether or not check if the devices are
mounted to prevent accidentally writing
to the root device
bind_ip 0.0.0.0 IP Address for server to bind to
bind_port 6002 Port for server to bind to
workers 1 Number of workers to fork
user swift User to run as
================== ========== =============================================
[account-server]
================== ============== ==========================================
Option Default Description
------------------ -------------- ------------------------------------------
use Entry point for paste.deploy for the account
server. For most cases, this should be
`egg:swift#account`.
log_name account-server Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
================== ============== ==========================================
[account-replicator]
================== ================== ======================================
Option Default Description
------------------ ------------------ --------------------------------------
log_name account-replicator Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
per_diff 1000
concurrency 8 Number of replication workers to spawn
run_pause 30 Time in seconds to wait between
replication passes
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
reclaim_age 604800 Time elapsed in seconds before an
account can be reclaimed
================== ================== ======================================
[account-auditor]
==================== =============== =======================================
Option Default Description
-------------------- --------------- ---------------------------------------
log_name account-auditor Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
interval 1800 Minimum time for a pass to take
max_container_count 100 Maximum containers randomly picked for
a given account audit
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
==================== =============== =======================================
[account-reaper]
================== =============== =========================================
Option Default Description
------------------ --------------- -----------------------------------------
log_name account-auditor Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Logging level
concurrency 25 Number of replication workers to spawn
interval 3600 Minimum time for a pass to take
node_timeout 10 Request timeout to external services
conn_timeout 0.5 Connection timeout to external services
================== =============== =========================================
--------------------------
Proxy Server Configuration
--------------------------
An example Proxy Server configuration can be found at
etc/proxy-server.conf-sample in the source code repository.
The following configuration options are available:
[DEFAULT]
============================ =============== =============================
Option Default Description
---------------------------- --------------- -----------------------------
bind_ip 0.0.0.0 IP Address for server to
bind to
bind_port 80 Port for server to bind to
swift_dir /etc/swift Swift configuration directory
workers 1 Number of workers to fork
user swift User to run as
cert_file Path to the ssl .crt
key_file Path to the ssl .key
============================ =============== =============================
[proxy-server]
============================ =============== =============================
Option Default Description
---------------------------- --------------- -----------------------------
use Entry point for paste.deploy for
the proxy server. For most
cases, this should be
`egg:swift#proxy`.
log_name proxy-server Label used when logging
log_facility LOG_LOCAL0 Syslog log facility
log_level INFO Log level
log_headers True If True, log headers in each
request
recheck_account_existence 60 Cache timeout in seconds to
send memcached for account
existence
recheck_container_existence 60 Cache timeout in seconds to
send memcached for container
existence
object_chunk_size 65536 Chunk size to read from
object servers
client_chunk_size 65536 Chunk size to read from
clients
memcache_servers 127.0.0.1:11211 Comma separated list of
memcached servers ip:port
node_timeout 10 Request timeout to external
services
client_timeout 60 Timeout to read one chunk
from a client
conn_timeout 0.5 Connection timeout to
external services
error_suppression_interval 60 Time in seconds that must
elapse since the last error
for a node to be considered
no longer error limited
error_suppression_limit 10 Error count to consider a
node error limited
rate_limit 20000.0 Max container level ops per
second
account_rate_limit 200.0 Max account level ops per
second
rate_limit_account_whitelist Comma separated list of
account name hashes to not
rate limit
rate_limit_account_blacklist Comma separated list of
account name hashes to block
completely
============================ =============== =============================
[auth]
============ =================================== ========================
Option Default Description
------------ ----------------------------------- ------------------------
use Entry point for paste.deploy
to use for auth. To
use the swift dev auth,
set to:
`egg:swift#auth`
ip 127.0.0.1 IP address of auth
server
port 11000 Port of auth server
ssl False If True, use SSL to
connect to auth
node_timeout 10 Request timeout
============ =================================== ========================
------------------------
Memcached Considerations
------------------------
Several of the Services rely on Memcached for caching certain types of
lookups, such as auth tokens, and container/account existence. Swift does
not do any caching of actual object data. Memcached should be able to run
on any servers that have available RAM and CPU. At Rackspace, we run
Memcached on the proxy servers. The `memcache_servers` config option
in the `proxy-server.conf` should contain all memcached servers.
-----------
System Time
-----------
Time may be relative but it is relatively important for Swift! Swift uses
timestamps to determine which is the most recent version of an object.
It is very important for the system time on each server in the cluster to
by synced as closely as possible (more so for the proxy server, but in general
it is a good idea for all the servers). At Rackspace, we use NTP with a local
NTP server to ensure that the system times are as close as possible. This
should also be monitored to ensure that the times do not vary too much.
----------------------
General Service Tuning
----------------------
Most services support either a worker or concurrency value in the settings.
This allows the services to make effective use of the cores available. A good
starting point to set the concurrency level for the proxy and storage services
to 2 times the number of cores available. If more than one service is
sharing a server, then some experimentation may be needed to find the best
balance.
At Rackspace, our Proxy servers have dual quad core processors, giving us 8
cores. Our testing has shown 16 workers to be a pretty good balance when
saturating a 10g network and gives good CPU utilization.
Our Storage servers all run together on the same servers. These servers have
dual quad core processors, for 8 cores total. We run the Account, Container,
and Object servers with 8 workers each. Most of the background jobs are run
at a concurrency of 1, with the exception of the replicators which are run at
a concurrency of 2.
The above configuration setting should be taken as suggestions and testing
of configuration settings should be done to ensure best utilization of CPU,
network connectivity, and disk I/O.
-------------------------
Filesystem Considerations
-------------------------
Swift is designed to be mostly filesystem agnostic--the only requirement
being that the filesystem supports extended attributes (xattrs). After
thorough testing with our use cases and hardware configurations, XFS was
the best all-around choice. If you decide to use a filesystem other than
XFS, we highly recommend thorough testing.
If you are using XFS, some settings that can dramatically impact
performance. We recommend the following when creating the XFS
partition::
mkfs.xfs -i size=1024 -f /dev/sda1
Setting the inode size is important, as XFS stores xattr data in the inode.
If the metadata is too large to fit in the inode, a new extent is created,
which can cause quite a performance problem. Upping the inode size to 1024
bytes provides enough room to write the default metadata, plus a little
headroom. We do not recommend running Swift on RAID, but if you are using
RAID it is also important to make sure that the proper sunit and swidth
settings get set so that XFS can make most efficient use of the RAID array.
We also recommend the following example mount options when using XFS::
mount -t xfs -o noatime,nodiratime,nobarrier,logbufs=8 /dev/sda1 /srv/node/sda
For a standard swift install, all data drives are mounted directly under
/srv/node (as can be seen in the above example of mounting /def/sda1 as
/srv/node/sda). If you choose to mount the drives in another directory,
be sure to set the `devices` config option in all of the server configs to
point to the correct directory.
---------------------
General System Tuning
---------------------
Rackspace currently runs Swift on Ubuntu Server 10.04, and the following
changes have been found to be useful for our use cases.
The following settings should be in `/etc/sysctl.conf`::
# disable TIME_WAIT.. wait..
net.ipv4.tcp_tw_recycle=1
net.ipv4.tcp_tw_reuse=1
# disable syn cookies
net.ipv4.tcp_syncookies = 0
# double amount of allowed conntrack
net.ipv4.netfilter.ip_conntrack_max = 262144
To load the updated sysctl settings, run ``sudo sysctl -p``
A note about changing the TIME_WAIT values. By default the OS will hold
a port open for 60 seconds to ensure that any remaining packets can be
received. During high usage, and with the number of connections that are
created, it is easy to run out of ports. We can change this since we are
in control of the network. If you are not in control of the network, or
do not expect high loads, then you may not want to adjust those values.
----------------------
Logging Considerations
----------------------
Swift is set up to log directly to syslog. Every service can be configured
with the `log_facility` option to set the syslog log facility destination.
We recommended using syslog-ng to route the logs to specific log
files locally on the server and also to remote log collecting servers.